What is cedar fever, its typical clinical presentation, and first‑line management?

Cedar Fever: Clinical Presentation and Management

What is Cedar Fever?

Cedar fever is seasonal allergic rhinoconjunctivitis caused by pollen from mountain cedar (Juniperus ashei), occurring predominantly in south-central Texas during winter months (December through February). 1, 2 Despite its name, cedar fever does not cause actual fever—the term reflects the severity of symptoms that can mimic a viral illness.

Clinical Presentation

Typical Symptoms

• Severe nasal congestion, rhinorrhea, sneezing, and postnasal drip 1
• Ocular symptoms including itching, tearing, and conjunctival injection 2
• Headache and facial pressure from sinus congestion 1
• Fatigue and malaise (the "fever" sensation without actual temperature elevation) 1

Key Distinguishing Features

• Symptoms occur exclusively during winter months (December-February) in endemic areas 2
• 34% of mountain cedar-allergic patients are monosensitized (allergic only to cedar pollen), while 66% have multiple aeroallergen sensitivities 1
• Monosensitized patients typically develop symptoms later in life (average age 39 years vs. 13 years for polysensitized patients) and require longer exposure periods (14.4 years vs. 5.69 years) before developing cedar pollinosis 1
• Monosensitized patients have significantly lower total IgE levels (84 IU/ml vs. 360 IU/ml) and less personal/family history of atopy (43% vs. 88%) 1

Diagnostic Confirmation

• Positive skin prick test to mountain cedar extract (1:20 w/v) confirms sensitization 1, 3
• Clinical history of winter-onset rhinoconjunctivitis symptoms in endemic areas (central Texas Hill Country) correlating with pollen exposure 2
• Pollen counts during peak season can reach 3,000-12,000 grains/m³, far exceeding the threshold for symptom induction 4

First-Line Management

Pharmacologic Treatment

For seasonal allergic rhinitis due to cedar pollen, clinicians should offer pre-/co-seasonal sublingual immunotherapy (SLIT) starting at least 8 weeks before the anticipated pollen season, as this provides the most effective disease-modifying treatment. 5

Immediate Symptomatic Relief

• Second-generation oral antihistamines (e.g., cetirizine, loratadine, fexofenadine) for rhinorrhea, sneezing, and ocular symptoms [General Medicine Knowledge]
• Intranasal corticosteroids (e.g., fluticasone, mometasone) as first-line therapy for nasal congestion and overall symptom control [General Medicine Knowledge]
• Intranasal antihistamines (e.g., azelastine) for rapid onset relief, particularly when combined with intranasal corticosteroids [General Medicine Knowledge]

Allergen Immunotherapy (Disease-Modifying)

Pre-/co-seasonal SLIT with mountain cedar extract should be initiated at least 8 weeks prior to the pollen season, with optimal efficacy achieved when treatment extends 4 months before season onset. 5

• Immunotherapy is equally effective in both monosensitized and polysensitized cedar-allergic patients, with no significant differences in clinical response 3
• Suppression of the late cutaneous response correlates significantly with cumulative allergen dose, post-seasonal IgG1 and IgG4 levels, and symptom improvement 3
• Sustained symptom reduction lasting 3-5 years after discontinuation of immunotherapy supports long-term disease modification 5
• In children, immunotherapy may prevent progression to asthma, with greatest benefit when started at younger ages (NNT=6 for children aged 5 vs. NNT=20 for children aged 12) 5

Non-Pharmacologic Measures

• Minimize outdoor exposure during peak pollen hours (typically morning) [General Medicine Knowledge]
• Keep windows closed and use HEPA air filtration indoors [General Medicine Knowledge]
• Shower and change clothing after outdoor activities to remove pollen [General Medicine Knowledge]
• Monitor local pollen counts to anticipate high-exposure days 2

Clinical Pearls and Pitfalls

Important Considerations

• The mountain cedar pollen season in central Texas is remarkably consistent year-to-year, with dependable and intense pollen density occurring every season over 18 consecutive years of monitoring 2
• The major allergen Jun a 1 shows high homology with Japanese cypress (Cha o 1) and Japanese cedar (Cry j 1) allergens, suggesting potential cross-reactivity in patients with exposure to multiple cedar species 6
• Patients with only cedar sensitivity (monosensitized) may represent a unique population possibly due to the carbohydrate nature of the main allergen, which may facilitate transport through respiratory mucosa 1

Common Pitfalls to Avoid

• Do not dismiss cedar allergy in patients without other atopic conditions—34% of cedar-allergic patients have no other sensitivities and may present later in life without typical atopic history 1
• Avoid starting SLIT less than 8 weeks before pollen season—inadequate preseasonal treatment duration reduces clinical efficacy 5
• Do not rely solely on late cutaneous response testing for monitoring immunotherapy without caution, as this procedure may result in systemic reactions 3
• Recognize that non-primed subjects in controlled pollen chamber studies show inadequate responses—priming runs are required to stimulate symptoms at levels sufficient for accurate assessment 4